using System;
using System.Globalization;
using System.Text.Json;
using System.Text.Json.Serialization;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using StackExchange.Redis;
using StellaOps.Scheduler.WebService.Options;

namespace StellaOps.Scheduler.WebService.GraphJobs.Events;

internal sealed class GraphJobEventPublisher : IGraphJobCompletionPublisher, IAsyncDisposable
{
    private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web)
    {
        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
    };

    private readonly IOptionsMonitor<SchedulerEventsOptions> _options;
    private readonly IRedisConnectionFactory _connectionFactory;
    private readonly ILogger<GraphJobEventPublisher> _logger;
    private readonly SemaphoreSlim _connectionGate = new(1, 1);

    private IConnectionMultiplexer? _connection;
    private bool _disposed;

    public GraphJobEventPublisher(
        IOptionsMonitor<SchedulerEventsOptions> options,
        IRedisConnectionFactory connectionFactory,
        ILogger<GraphJobEventPublisher> logger)
    {
        _options = options ?? throw new ArgumentNullException(nameof(options));
        _connectionFactory = connectionFactory ?? throw new ArgumentNullException(nameof(connectionFactory));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    public async Task PublishAsync(GraphJobCompletionNotification notification, CancellationToken cancellationToken)
    {
        if (notification is null)
        {
            throw new ArgumentNullException(nameof(notification));
        }

        var options = _options.CurrentValue?.GraphJobs ?? new GraphJobEventsOptions();
        if (!options.Enabled)
        {
            _logger.LogDebug("Graph job events disabled; skipping emission for {JobId}.", notification.Job.Id);
            return;
        }

        if (!string.Equals(options.Driver, "redis", StringComparison.OrdinalIgnoreCase))
        {
            _logger.LogWarning(
                "Graph job events configured with unsupported driver '{Driver}'. Falling back to logging.",
                options.Driver);
            LogEnvelope(notification);
            return;
        }

        try
        {
            var database = await GetDatabaseAsync(options, cancellationToken).ConfigureAwait(false);
            var envelope = GraphJobEventFactory.Create(notification);
            var payload = JsonSerializer.Serialize(envelope, SerializerOptions);
            var entries = new[]
            {
                new NameValueEntry("event", payload),
                new NameValueEntry("kind", envelope.Kind),
                new NameValueEntry("tenant", envelope.Tenant),
                new NameValueEntry("occurredAt", envelope.Timestamp.ToString("O", CultureInfo.InvariantCulture)),
                new NameValueEntry("jobId", notification.Job.Id),
                new NameValueEntry("status", notification.Status.ToString())
            };

            var streamKey = string.IsNullOrWhiteSpace(options.Stream) ? "stella.events" : options.Stream;
            var publishTask = CreatePublishTask(database, streamKey, entries, options.MaxStreamLength);

            if (options.PublishTimeoutSeconds > 0)
            {
                var timeout = TimeSpan.FromSeconds(options.PublishTimeoutSeconds);
                await publishTask.WaitAsync(timeout, cancellationToken).ConfigureAwait(false);
            }
            else
            {
                await publishTask.ConfigureAwait(false);
            }

            _logger.LogDebug("Published graph job event {JobId} to stream {Stream}.", notification.Job.Id, streamKey);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to publish graph job completion for {JobId}; logging payload instead.", notification.Job.Id);
            LogEnvelope(notification);
        }
    }

    private Task<RedisValue> CreatePublishTask(IDatabase database, string streamKey, NameValueEntry[] entries, long maxStreamLength)
    {
        if (maxStreamLength > 0)
        {
            var clamped = (int)Math.Min(maxStreamLength, int.MaxValue);
            return database.StreamAddAsync(streamKey, entries, maxLength: clamped, useApproximateMaxLength: true);
        }

        return database.StreamAddAsync(streamKey, entries);
    }

    private async Task<IDatabase> GetDatabaseAsync(GraphJobEventsOptions options, CancellationToken cancellationToken)
    {
        cancellationToken.ThrowIfCancellationRequested();

        if (_connection is { IsConnected: true })
        {
            return _connection.GetDatabase();
        }

        await _connectionGate.WaitAsync(cancellationToken).ConfigureAwait(false);
        try
        {
            if (_connection is null || !_connection.IsConnected)
            {
                var configuration = ConfigurationOptions.Parse(options.Dsn);
                configuration.AbortOnConnectFail = false;

                if (options.DriverSettings.TryGetValue("clientName", out var clientName) && !string.IsNullOrWhiteSpace(clientName))
                {
                    configuration.ClientName = clientName;
                }

                if (options.DriverSettings.TryGetValue("ssl", out var sslValue) && bool.TryParse(sslValue, out var ssl))
                {
                    configuration.Ssl = ssl;
                }

                if (options.DriverSettings.TryGetValue("password", out var password) && !string.IsNullOrWhiteSpace(password))
                {
                    configuration.Password = password;
                }

                _connection = await _connectionFactory.ConnectAsync(configuration, cancellationToken).ConfigureAwait(false);
                _logger.LogInformation("Connected graph job publisher to Redis stream {Stream}.", options.Stream);
            }
        }
        finally
        {
            _connectionGate.Release();
        }

        return _connection!.GetDatabase();
    }

    private void LogEnvelope(GraphJobCompletionNotification notification)
    {
        var envelope = GraphJobEventFactory.Create(notification);
        var json = JsonSerializer.Serialize(envelope, SerializerOptions);
        _logger.LogInformation("{EventJson}", json);
    }

    public async ValueTask DisposeAsync()
    {
        if (_disposed)
        {
            return;
        }

        _disposed = true;

        if (_connection is not null)
        {
            try
            {
                await _connection.CloseAsync();
            }
            catch (Exception ex)
            {
                _logger.LogDebug(ex, "Error while closing graph job Redis connection.");
            }

            _connection.Dispose();
        }

        _connectionGate.Dispose();
    }
}